The present invention relates to a method for assigning channel in a mobile communication system, which increases the number of usable channels using the special method of channel assigning that makes possible the efficient use of the marginal resource in a DSP.
The Digital Signal Processor (DSP) in the mobile communication system performs compression and decompression of voice, namely, vocoding. In accordance with the technological progress in the semiconductor integrated circuit, most DSP chips became to adopt the multi-channel technology that simultaneously vocodes several channels in a DSP. In the multi-channel DSP technology, the present invention brings up a method that increases the efficiency of the DSP.
FIG. 1 is a block diagram showing a conventional mobile communication system that includes a mobile station 1, a base station 2, a base station controller 3, a mobile switching center (MSC) 4, a fixed terminal 5.
In case that a mobile station subscriber starts to call a fixed terminal subscriber, after a call set-up between the two terminals, the mobile station subscriber inputs her voice into the mobile station 1. Then the mobile station 1 changes the input voice signal into Qualcomm Code Exited Linear Predictive (QCELP) data and transfers the QCELP data to a Transcoder and Selector Bank (TSB) 3xe2x80x2 in the base station controller 3. The QCELP data is voice packet data. Next, the TSB 3xe2x80x2 transfers the QCELP data to a vocoder 3xe2x80x3 in the base station controller 3. The vocoder 3xe2x80x3 decodes QCELP data to PCM (Pulse Code Modulation) data and then sends the PCM data through a mobile switching center (MSC) 4 to the fixed terminal 5. By the above process, the fixed terminal subscriber finally hears the voice inputted by the mobile station subscriber.
In the mean time, in case that a fixed terminal subscriber starts to call a mobile station subscriber, after a call set-up between the two terminals, the fixed terminal subscriber inputs her voice into the fixed terminal 5, which encodes the input voice signal to PCM data and transfers the PCM data through the MSC 4 to a vocoder 3xe2x80x3 in the base station controller. The vocoder 3xe2x80x3 encodes the PCM data to QCELP data and transfers the QCELP data to the mobile station 1 through a TSB 3xe2x80x2 and a base transceiver station 2. By the above process, the mobile station subscriber finally hears the voice inputted by the fixed terminal subscriber. Even though FIG. 1 shows only a QCELP vocoding algorithm for a vocoder, the algorithm can be replaced by an Enhanced Variable Rate Coder (ECRC) vocoding algorithm.
The vocoder in FIG. 1 performs two more operations of bypass and data service in addition to vocoding, and each operation is as follows.
First, the vocoding operation is used to increase channel capacity in the Mobile Communication System. Vocoding is the operation that encodes PCM data to packet data such as QCELP and decodes packet data to PCM data. The three kinds of vocoding algorithms such as QCELP 8K, QCELP 13K and EVRC is used for Code Division Multiple Access (CDMA), and among them, EVRC that has the highest complexity is used to produce the maximum usable channels per DSP in the multi-channel DSP technology.
Second, bypass is the operation to prevent double vocoding, which performs compression and decompression twice, when a call set-up is established between two mobile stations. Because vocoding algorithms make a loss in voice quality whenever they are performed, the repetitive vocoding makes worse the quality of a decompressed voice from a compressed voice, and makes the decompressed voice different from an original voice. Therefore a compressed packet data, in the case of a call between two mobile station subscribers, is bypassed without additional compression by a vocoder 3xe2x80x3. So the bypass operation, which decreases the repetitive use of the vocoding operation, is used to prevent voice quality from dropping off. It performs the function in less complexity (about 10% of the vocoding operation) than the vocoding operation.
Lastly, the data service operation performs an adjustment function using ISLP (Inter System Link Protocol) between a mobile station and an IWF (Inter Working Function). The data service operation performs the function in less complexity (about 30% of the vocoding operation) than the vocoding operation.
Next, the prior channel assigning method is as the following.
In the multi-channel technology, a DSP can simultaneously vocode several channels, and each channel has three operation modes of vocoding, bypass and data service. At this time, based on the vocoding mode that has the highest complexity among three operation modes, the number of the maximum usable channels is decided.
In order to set-up a call, regardless of the operation mode, the call control processor (CCP) assigns the call to a usable channel. Next, the CCP decides an operation mode for the call and inform the decision to a DSP. Then the DSP operates the mode decided by the CCP for the usable channel.
In such a multi-channel environment, the number of the maximum usable channels can be calculated under the assumption that all channels will be operated in the vocoding mode. At this time, a DSP will have a marginal resource which cannot accommodate one full vocoding channel and the marginal resource has been wasted in the prior art.
The object of the present invention is to provide a channel assigning method that increases the number of usable channels of a DSP by assigning the bypass mode and the data service mode to the marginal channel not enough to assign vocoding mode which needs more resources of DSP.
Hereinafter, the channel assigning method of the present invention is briefly explained.
The first step of the channel assigning method is to identify what an input call is among a call the requesting vocoding operation, a call requesting the bypass operation, and a call requesting the data service operation.
The second step is to decide whether there is a usable dedicated channel for the operation mode of the input call identified at the first step; (a) if there is, the input call is assigned to the dedicated channel of the same operation mode as identified at the first step; and (b) if there is not, but a complex channel is available for the call, the input call is assigned to a complex channel corresponding to the dedicated channel.
Additionally, the present invention, in case that an input call is the call requesting vocoding, has a step comparing the number of the already used complex channels to the number of maximum usable complex channels; (a) in accordance with the compared result, if the number of the maximum usable complex channels is not equal to the number of the already used complex channels, the call requesting vocoding is assigned to a complex channel; (b) if the number of the maximum usable complex channels is equal to the number of the already used complex channels, the call requesting vocoding is rejected to be assigned on a complex channel.
Next, the present invention, in case that an input call is the call requesting bypass, has a step comparing the number of the maximum usable bypass channels to the number of the already used bypass channels; (a) in accordance with the compared result, if the number of the already used bypass channels is not equal to the number of the maximum usable bypass channels, the call requesting bypass is assigned to a bypass channel; (b) if the number of the already used bypass channels is equal to the maximum usable bypass channels, the call requesting bypass, through the decision of whether a complex channel is available, is assigned to the complex channel.
Next, the present invention, in case that an input call is the call requesting data service, has a step comparing the number of the maximum usable data service channels to the number of the already used data service channels; (a) in accordance with the compared result, if the number of the already used data service channels is not equal to the number of the maximum usable data service channels, the call requesting data service is assigned to a data service channel; (b) if the numbers of the already used data service channels and the maximum usable data service channels are equal, the call requesting data service, through the decision of whether a complex channel is available, is assigned to the complex channel.